The present invention relates generally to methods and apparatus for disinfecting and sterilizing fluids using an ultraviolet light source, and more particularly to a novel ultraviolet lamp which can be used in a wide variety of harsh environments to kill micro organisms living in fluids.
The use of ultraviolet light sources for sterilizing and disinfecting fluids is well-known in the art. A typical ultraviolet light source has two primary parts, the tube and the base. The tube usually comprises a soft glass or quartz casing which holds a vaporizable material, such as mercury, and a starting gas and/or stabilizing gas, such as argon, neon, zeon or the like. The tube also includes one or more electrodes, which when provided with power, excite the gas and the vaporizable material. The excited vaporizable material causes a plasma field which generates the ultraviolet light.
In addition to the tube, an ultraviolet light source typically comprises a base, which is designed to hold the tube in place during operation, but which allows the tube to be removed and replaced when necessary.
While ultraviolet light sources have been used for some time for sterilization purposes, a problem with the ultraviolet light sources currently known in the art is that they are fragile and typically cannot handle the harsh environments in which they must be used. For example, because the prior art ultraviolet light sources are made of soft glass or quartz, the lamps tend to break easily. In addition, because of the adhesive nature of the soft glass or quartz casing, residue and other impurities tend to build up on the lamps over time, affecting the performance of the lamp. Finally, the prior art ultraviolet light sources have a tendency to be expensive and difficult to maintain. Therefore, what is needed is an inexpensive, impact resistant ultraviolet light source, which can be used for sterilization purposes, can be easily introduced into existing systems, is thermally stable in cold or hot fluids including air, and does not require significant modification of the system.
According to one embodiment of the invention, an ultraviolet light source which includes an ultraviolet light bulb or lamp, a power source for providing power to the ultraviolet light bulb, and a non-glass or non-quartz protective sleeve which surrounds the ultraviolet light bulb. The ultraviolet light bulb preferably includes a casing for holding a starting gas and a vaporizable material, and at least one electrode electrically coupled to the power source for exciting the starting gas and the vaporizable material within the casing. In accordance with one embodiment of the present invention, the casing is made of soft glass or quartz material, and the protective sleeve is a UV transparent or transmissive material. For example, the protective sleeve may comprise a fluoropolymer sleeve which surrounds the soft glass or quartz casing. The fluoropolymer sleeve may comprise any suitable fluoropolymer material, such as the Teflon(copyright) family of products like PTFE, FEP, PFA, AF, Tefzel(copyright) ETFE, and all other Teflon(copyright) products developed in the future. In addition, some silicone based materials, like silicone polymers, and other UV transmissive non-glass materials can be used for the protective sleeve.
In accordance with another embodiment of the present invention, instead of the casing being a quartz or soft glass casing surrounded by a fluoropolymer sleeve, the casing itself may be made of the fluoropolymer material. Thus, instead of two layers for the casing (i.e., the soft glass or quartz, and the fluoropolymer sleeve), a single layer fluoropolymer or other UVC transparent material casing can be used.
In accordance with yet another embodiment in the present invention, the protective sleeve may comprise a permanent sleeve surrounding the ultraviolet light source, or the protective sleeve may comprise a removable container, so that the ultraviolet light bulb can be replaced when it burns out or malfunctions. In the case where the protective sleeve is permanent, the sleeve may preferably comprise a fluoropolymer, silicone or other UV transmissive material which is heat shrunk around the ultraviolet light bulb or the entire light source, or the fluoropolymer, silicone or other UV transmissive material is applied by pressing it onto the light source, or dipping the light source into a liquid form of the material.
The protective sleeve seals in the soft glass or quartz casing, protecting it from breakage. However, in situations where the glass or quartz does break, the protective sleeve contains the glass particles and harmful mercury vapor material so that the environment in which the lamp is used is not exposed to the glass and mercury materials. Said another way, the protective sleeve hermetically seals the lamp. For example, if the lamp is used in a drinking water supply tank, and the glass or quartz casing of the lamp happens to break, the protective sleeve prevents the glass or quartz particles, as well as the harmful mercury within the lamp from contaminating the drinking water supply. In addition, the protective sleeve preferably acts as a thermal insulator, which helps keep the ultraviolet light""s plasma thermally stable.
The ultraviolet light source of the present invention may be used for sterilizing and/or disinfecting fluids, as well as the surfaces of containers, pipes, ducts, or other suitable devices with which the fluid contacts. As one skilled in the art will appreciate, the term fluid includes air, water and other suitable fluids. The ultraviolet light which illuminates from the ultraviolet light source may comprise any suitable UV light, such as UVA, UVB, UVC, or the like. However, in accordance with one embodiment of the present invention, the light is a UVC light (e.g., light having a wavelength between about 180 nm and about 325 nm), which is good for killing living organisms, such as molds, bacteria, viruses, and the like. Because of the resilient nature of the protective sleeve of the present invention, the ultraviolet light source can be used in virtually any environment where it is beneficial to disinfect and/or sterilize a fluid.
A more complete understanding of the present invention may be derived by referring to the detailed description of preferred embodiments and claims when considered in connection with the figures, wherein like reference numbers refer to similar items throughout the figures.